Liquid ejection apparatus

ABSTRACT

An actuator device includes: an actuator including a first contact; and a wire member including a second contact connected to the first contact with a conductive adhesive including a conductive particle. One of the first contact and the second contact is a particular contact. The other of the first contact and the second contact is a specific contact. At least two protrusions and at least one recess are formed on and in the particular contact. The at least two protrusions are arranged in a first direction. The at least one recess is interposed between the at least two protrusions. The particular contact is joined to the specific contact with the conductive adhesive provided in the at least one recess, in a state in which each of the at least two protrusions is in contact with the specific contact.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 16/055,291, filed Aug. 6, 2018, now issued U.S. Pat. No.10,236,434, which is a continuation of U.S. patent application Ser. No.15/472,056, filed Mar. 28, 2017, now issued U.S. Pat. No. 10,069,058,which further claims priority from Japanese Patent Application No.2016-189997, filed on Sep. 28, 2016, the disclosure of all of which isherein incorporated by reference in their entirety.

BACKGROUND

The following disclosure relates to an actuator device, a liquidejection apparatus, and a connection structure of a wire member.

There is known a charge plate for selectively charging ink to be ejectedby an ink-jet head through its orifices. An insulated base of the chargeplate is provided with charge electrodes and lead wires corresponding tothe respective charge electrodes. Contacts are provided on end portionsof the respective lead wires. A wire member including wires (conductionbands) are joined to an end portion of the insulated base on which thecontacts provided on the lead wires are disposed.

The wire member and the insulated base of the charge plate are connectedto each other with a conductive adhesive formed of an anisotropicconductive material, for example. The conductive adhesive is athermosetting adhesive containing conductive particles. Portions of thewire member and the insulated base of the charge plate which are to bejoined to each other are heated and pressurized in a state in which theconductive adhesive having not been hardened yet is interposed betweenthe wire member and the insulated base of the charge plate. In thisprocess, the contacts provided on the charge plate and the wiresprovided on the wire member are electrically connected to each otherthrough the conductive particles. Also, the adhesive is hardened byheating, which mechanically joins the wire member to the charge plate.

SUMMARY

In the joining with the conductive adhesive, the contacts of the twocomponents are electrically connected to each other through theconductive particles contained in the thermosetting adhesive. In thisprocess, however, the conductive particles contained in the conductiveadhesive in some cases flow out to areas around the contacts togetherwith the adhesive, leading to shorts between adjacent contacts due tothe conductive particles having flowed out. Decreased density of theconductive particles may reduce occurrences of the shorts. However, thesmaller number of the conductive particles easily causes a situation inwhich no conductive particles are provided between two contacts, whichmay lead to poor connection.

Accordingly, an aspect of the disclosure relates to a technique ofincreasing reliability of electric connection between two contactswithout increase in density of conductive particles in connection of thetwo contacts using a conductive adhesive.

In one aspect of the disclosure, an actuator device includes: anactuator including at least one first contact; and a wire memberincluding at least one second contact respectively connected to the atleast one first contact with a conductive adhesive including aconductive particle. One of (i) each of the at least one first contactand (ii) each of the at least one second contact is each of at least oneparticular contact, and another of (i) each of the at least one firstcontact and (ii) each of the at least one second contact is each of atleast one specific contact. At least two protrusions and at least onerecess are formed on and in the at least one particular contact. The atleast two protrusions are arranged in a first direction parallel with aplacement surface of each of the at least one particular contact. The atleast one recess is interposed between the at least two protrusions. Theat least one particular contact is respectively joined to the at leastone specific contact with the conductive adhesive provided in the atleast one recess, in a state in which each of the at least twoprotrusions is in contact with a corresponding one of the at least onespecific contact.

In another aspect of the disclosure, a liquid ejection apparatusincludes: a passage definer defining therein at least one pressurechamber; a vibration layer covering the at least one pressure chamber;at least one piezoelectric element disposed on the vibration layer so asto respectively overlap the at least one pressure chamber; at least onefirst contact respectively drawn from the at least one piezoelectricelement; and a wire member including at least one second contactrespectively connected to the at least one first contact with aconductive adhesive including a conductive particle. One of (i) each ofthe at least one first contact and (ii) each of the at least one secondcontact is each of at least one particular contact, and another of (i)each of the at least one first contact and (ii) each of the at least onesecond contact is each of at least one specific contact. At least twoprotrusions and at least one recess are formed on and in the at leastone particular contact. The at least two protrusions are arranged in afirst direction parallel with a placement surface of each of the atleast one particular contact, the at least one recess being interposedbetween the at least two protrusions. The at least one particularcontact is respectively joined to the at least one specific contact withthe conductive adhesive provided in the at least one recess, in a statein which each of the at least two protrusions is in contact with acorresponding one of the at least one specific contact.

Yet another aspect of the disclosure relates to a connection structurefor connecting at least one first contact and at least one secondcontact of a wire member respectively to each other with a conductiveadhesive. One of (i) each of the at least one first contact and (ii)each of the at least one second contact is each of at least oneparticular contact. Another of (i) each of the at least one firstcontact and (ii) each of the at least one second contact is each of atleast one specific contact. At least two protrusions and at least onerecess are formed on and in the at least one particular contact. The atleast two protrusions are arranged in a first direction parallel with aplacement surface of each of the at least one particular contact. The atleast one recess is interposed between the at least two protrusions. Theat least one particular contact is respectively joined to the at leastone specific contact with the conductive adhesive provided in the atleast one recess, in a state in which each of the at least twoprotrusions is in contact with a corresponding one of the at least onespecific contact.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features, advantages, and technical and industrialsignificance of the present disclosure will be better understood byreading the following detailed description of the embodiment, whenconsidered in connection with the accompanying drawings, in which:

FIG. 1 is a schematic plan view of a printer according to the presentembodiment;

FIG. 2 is a plan view of an ink-jet head;

FIG. 3 is an enlarged view of a rear end portion of the ink-jet head inFIG. 2;

FIG. 4 is an enlarged view of an area A in FIG. 3;

FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4;

FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 4;

FIG. 7 is a plan view of a driving contact of a piezoelectric actuator;

FIG. 8A is a cross-sectional view of joined portions of thepiezoelectric actuator and a COF, taken along line A-A in FIG. 7, andFIG. 8B is a cross-sectional view of the joined portions, taken alongline B-B in FIG. 7;

FIG. 9 is a plan view of a ground contact of the piezoelectric actuator;

FIG. 10A is a cross-sectional view of the joined portions of thepiezoelectric actuator and the COF, taken along line A-A in FIG. 9, andFIG. 10B is a cross-sectional view of the joined portions, taken alongline B-B in FIG. 9;

FIGS. 11A-11F are views illustrating a first portion of a process ofproducing the ink-jet head;

FIGS. 12G-12I are views illustrating a second portion of the process ofproducing the ink-jet head;

FIGS. 13A and 13B are cross-sectional views each illustrating joinedportions of a piezoelectric actuator and a COF of an ink-jet head in acorresponding modification;

FIGS. 14A-14D are cross-sectional views each illustrating joinedportions of a piezoelectric actuator and a COF of an ink-jet head in acorresponding modification; and

FIG. 15 is a cross-sectional view illustrating joined portions of apiezoelectric actuator and a COF of an ink-jet head in anothermodification.

DETAILED DESCRIPTION OF THE EMBODIMENT

Hereinafter, there will be described an embodiment by reference to thedrawings. First, there will be explained an overall configuration of anink-jet printer 1 with reference to FIG. 1. The direction in which arecording sheet 100 is conveyed in FIG. 1 is defined as the front andrear direction of the printer 1. The widthwise direction of therecording sheet 100 is defined as the right and left direction of theprinter 1. The direction orthogonal to the front and rear direction andthe right and left direction and perpendicular to the sheet surface ofFIG. 1 is defined as the up and down direction of the printer 1.

Overall Configuration of Printer

As illustrated in FIG. 1, the ink-jet printer 1 includes a carriage 3,an ink-jet head 4, a conveying mechanism 5, and a controller 6.

The carriage 3 is mounted on guide rails 10, 11 extending in the rightand left direction (hereinafter may also be referred to as “scanningdirection”). The carriage 3 is joined to a carriage driving motor 15 viaan endless belt 14. The carriage 3 is driven by the motor 15 andreciprocated in the scanning direction over the recording sheet 100conveyed on a platen 2.

The ink-jet head 4 is mounted on the carriage 3. Inks of four colors,namely, black, yellow, cyan, and magenta, are supplied to the ink-jethead 4 respectively via tubes, not illustrated, from four ink cartridges17 held by a holder 7. While moving in the scanning direction with thecarriage 3, the ink-jet head 4 ejects the inks from a multiplicity ofnozzles 24 (see FIGS. 2-6) onto the recording sheet 100 conveyed on theplaten 2.

The conveying mechanism 5 includes two conveying rollers 18, 19configured to convey the recording sheet 100 on the platen 2 in thefront direction (hereinafter may also be referred to as “conveyingdirection”).

The controller 6 controls devices including the ink-jet head 4 and thecarriage driving motor 15 to print an image on the recording sheet 100based on a print instruction received from an external device such as apersonal computer (PC).

Detailed Configuration of Ink-Jet Head

There will be next explained a configuration of the ink-jet head 4 withreference to FIGS. 2-6. It is noted that FIGS. 3 and 4 omit illustrationof a protector 23 illustrated in FIG. 2.

In the present embodiment, the ink-jet head 4 ejects the inks of thefour colors (black, yellow, cyan, and magenta). As illustrated in FIGS.2-6, the ink-jet head 4 includes a nozzle plate 20, a passage definer21, and an actuator device 25 including a piezoelectric actuator 22. Inthe present embodiment, the actuator device 25 does not indicate onlythe piezoelectric actuator 22 but includes not only the piezoelectricactuator 22 but also the protector 23 and chip-on-films (COFs) 50disposed on the piezoelectric actuator 22. Each of the COFs 50 is oneexample of a wire member.

Nozzle Plate

The nozzle plate 20 is formed of silicon, for example. The nozzle plate20 has the nozzles 24 arranged in the conveying direction. That is, thefront and rear direction coincides with a direction in which the nozzles24 are arranged (hereinafter also referred to as “nozzle arrangementdirection”).

More specifically, as illustrated in FIGS. 2 and 3, the nozzle plate 20has four nozzle groups 27 arranged in the scanning direction. The fournozzle groups 27 are for ejection of the different inks, respectively.Each of the nozzle groups 27 is constituted by right and left nozzlerows 28. In each of the nozzle rows 28, the nozzles 24 are arranged atintervals P. Positions of the nozzles 24 are displaced by P/2 in theconveying direction between the two nozzle rows 28. That is, the nozzles24 are arranged in two rows in a staggered configuration in each nozzlegroup 27.

In the following explanation, one of suffixes k, y, c, and m may beselectively added to the reference numbers of components of the ink-jethead 4 to indicate their respective correspondences with one of theblack, yellow, cyan, and magenta inks. For example, the wording “nozzlegroups 27 k” indicates the nozzle group 27 for the black ink.

Passage Definer

The passage definer 21 is a base plate formed of silicon single crystal.As illustrated in FIGS. 3-6, the passage definer 21 has pressurechambers 26 communicating with the respective nozzles 24. Each of thepressure chambers 26 has a rectangular shape elongated in the scanningdirection in plan view. The pressure chambers 26 are arranged in theconveying direction so as to correspond to the arrangement of thenozzles 24. The pressure chambers 26 are arranged in eight pressurechamber rows, each two of which correspond to one of the four inkcolors. A lower surface of the passage definer 21 is covered with thenozzle plate 20. An outer end portion of each of the pressure chambers26 in the scanning direction overlaps a corresponding one of the nozzles24.

A vibration layer 30 of the piezoelectric actuator 22, which will bedescribed below, is disposed on an upper surface of the passage definer21 so as to cover the pressure chambers 26. The vibration layer 30 isnot limited in particular as long as the vibration layer 30 is aninsulating layer covering the pressure chambers 26. In the presentembodiment, the vibration layer 30 is formed by oxidation or nitridingof a surface of the base plate formed of silicon. The vibration layer 30has ink supply holes 30 a at areas each covering an end portion of acorresponding one of the pressure chambers 26 in the scanning direction(which end portion is located on an opposite side of the pressurechamber 26 from the nozzle 24).

For each ink color, the ink is supplied from a corresponding one of fourreservoirs 23 b formed in the protector 23 to the pressure chambers 26through the respective ink supply holes 30 a. When ejection energy isapplied to the ink in each of the pressure chambers 26 by acorresponding one of piezoelectric elements 31 of the piezoelectricactuator 22 which will be described below, an ink droplet is ejectedfrom the nozzle 24 communicating with the pressure chamber 26.

Actuator Device

The actuator device 25 is disposed on the upper surface of the passagedefiner 21. The actuator device 25 includes: the piezoelectric actuator22 including the piezoelectric elements 31; the protector 23; and thetwo COFs 50.

The piezoelectric actuator 22 is disposed on the entire upper surface ofthe passage definer 21. As illustrated in FIGS. 3 and 4, thepiezoelectric actuator 22 includes the piezoelectric elements 31arranged so as to overlap the respective pressure chambers 26. Thepiezoelectric elements 31 are arranged in the conveying direction so asto correspond to the arrangement of the pressure chambers 26 andconstitute eight piezoelectric element rows 38. A plurality of drivingcontacts 46 and two ground contacts 47 are drawn out leftward from leftfour of the piezoelectric element rows 38, and as illustrated in FIGS. 2and 3 the contacts 46, 47 are disposed on a left end portion of thepassage definer 21. A plurality of driving contacts 46 and two groundcontacts 47 are drawn out rightward from right four of the piezoelectricelement rows 38, and the contacts 46, 47 are disposed on a right endportion of the passage definer 21. The structure of the piezoelectricactuator 22 will be described below in detail.

The protector 23 is disposed on an upper surface of the piezoelectricactuator 22 so as to cover the piezoelectric elements 31. Specifically,the protector 23 includes eight recessed protecting portions 23 arespectively covering the eight piezoelectric element rows 38. Asillustrated in FIG. 2, the protector 23 does not cover right and leftend portions of the piezoelectric actuator 22, so that the drivingcontacts 46 and the ground contacts 47 are exposed from the protector23. The protector 23 has the reservoirs 23 b connected to the respectiveink cartridges 17 held by the holder 7. The ink in each of thereservoirs 23 b is supplied to the pressure chambers 26 throughrespective ink supply passages 23 c and the respective ink supply holes30 a formed in the vibration layer 30.

Each of the COFs 50 illustrated in FIGS. 2-5 is a flexible wire (lead)member including a base 56 formed of insulating material such as apolyimide film. A driver IC 51 is mounted on the base 56. One endportions of the respective two COFs 50 are connected to the controller 6(see FIG. 1) of the printer 1. The other end portions of the respectivetwo COFs 50 are respectively joined to right and left end portions ofthe piezoelectric actuator 22. As illustrated in FIG. 4, each of theCOFs 50 includes ground wires 53 and a plurality of individual wires 52connected to the respective driver ICs 51. Individual contacts 54 areprovided on distal end portions of the respective individual wires 52and connected to the respective driving contacts 46 of the piezoelectricactuator 22. Ground contacts 55 are provided on distal end portions ofthe respective ground wires 53 and connected to the respective groundcontacts 47 of the piezoelectric actuator 22. Each of the driver ICs 51outputs a drive signal to a corresponding one of the piezoelectricelements 31 of the piezoelectric actuator 22 via a corresponding one ofthe individual contacts 54 and a corresponding one of the drivingcontacts 46. While the two ground contacts 47 are provided for each ofthe COFs 50 in the present embodiment, the following explanation will begiven for one of the ground contacts 47 for simplicity unless otherwiserequired.

Detailed Structure of Piezoelectric Actuator

The piezoelectric actuator 22 includes: the vibration layer 30 formed onthe upper surface of the passage definer 21; and the piezoelectricelements 31 disposed on an upper surface of the vibration layer 30. Forsimplicity, FIGS. 3 and 4 omit illustration of a protecting layer 40, aninsulating layer 41, and a wire protecting layer 43 illustrated in FIGS.5 and 6.

As illustrated in FIGS. 3-6, the piezoelectric elements 31 are arrangedon the upper surface of the vibration layer 30 so as to overlap therespective pressure chambers 26. That is, the piezoelectric elements 31are arranged in the conveying direction so as to correspond to thearrangement of the pressure chambers 26. As a result, in accordance withthe arrangement of the nozzles 24 and the pressure chambers 26, thepiezoelectric elements 31 constitute the eight piezoelectric elementrows 38, each two of which correspond to one of the four ink colors. Itis noted that a group of the piezoelectric elements 31 of the twopiezoelectric element rows 38 corresponding to each of the four inkcolors will be referred to as “piezoelectric element group 39”. Asillustrated in FIG. 3, the four piezoelectric element groups 39 k, 39 y,39 c, 39 m respectively corresponding to the four ink colors arearranged in the scanning direction.

Each of the piezoelectric elements 31 includes a first electrode 32, apiezoelectric layer 33, and a second electrode 34 disposed in this orderfrom a lower side over the vibration layer 30.

As illustrated in FIGS. 5 and 6, the first electrode 32 is formed at anarea opposed to the pressure chamber 26 formed in the vibration layer30. As illustrated in FIG. 6, each adjacent two of the first electrodes32 of the respective piezoelectric elements 31 are connected to eachother by an electrically conductive portion 35 disposed between thepiezoelectric elements 31. In other words, the first electrodes 32 andthe electrically conductive portions 35 connecting the first electrodes32 to each other constitute a common electrode 36 that coverssubstantially the entire upper surface of the vibration layer 30. Thecommon electrode 36 is formed of platinum (Pt), for example. Thethickness of the common electrode 36 is 0.1 μm, for example. It is notedthat the wording “conduct” and “conductive” in the present specificationprincipally means “electrically conduct” and “electrically conductive”.

The piezoelectric layer 33 is formed of a piezoelectric material such aslead zirconate titanate (PZT), for example. The piezoelectric layer 33may be formed of a non-lead piezoelectric material not containing lead.The thickness of the piezoelectric layer 33 is ranged between 1.0 μm and2.0 μm, for example.

As illustrated in FIGS. 3, 4, and 6, in the present embodiment, thepiezoelectric layers 33 of the respective piezoelectric elements 31 areconnected to each other in the conveying direction to form a rectangularpiezoelectric member 37 elongated in the conveying direction. That is,the eight piezoelectric members 37 constituted by the piezoelectriclayers 33 respectively corresponding to the eight pressure chamber rowsare disposed on the common electrode 36 covering the vibration layer 30.

The second electrodes 34 are disposed on upper surfaces of therespective piezoelectric layers 33. Each of the second electrodes 34 hasa rectangular shape in plan view which is one size smaller than each ofthe pressure chambers 26. The second electrodes 34 respectively overlapcentral portions of the respective pressure chambers 26. Unlike thefirst electrodes 32, the second electrodes 34 of the respectivepiezoelectric elements 31 are separated and spaced apart from eachother. That is, the second electrodes 34 are individual electrodesprovided for individually for the respective piezoelectric elements 31.The second electrodes 34 are formed of iridium (Ir) or platinum (Pt),for example. The thickness of each of the second electrodes 34 is 0.1μm, for example.

As illustrated in FIGS. 5 and 6, the piezoelectric actuator 22 includesthe protecting layer 40, the insulating layer 41, wires 42, and the wireprotecting layer 43.

As illustrated in FIG. 5, the protecting layer 40 is disposed so as tocover a surface of the piezoelectric member 37 except central portionsof the respective second electrodes 34. One of main purposes of theprotecting layer 40 is preventing ingress of water from air into thepiezoelectric layers 33. The protecting layer 40 is formed of a materialhaving low permeability such as oxides and nitrides, for example.Examples of the oxides include alumina (Al2O3), silicon oxide (SiOx),and tantalum oxide (TaOx). Examples of the nitrides include siliconnitride (SiN).

The insulating layer 41 is formed on an upper side of the protectinglayer 40. A material of the insulating layer 41 is not limited inparticular. For example, the insulating layer 41 is formed of silicondioxide (SiO2). This insulating layer 41 is provided for increasinginsulation between the common electrode 36 and the wires 42 connected tothe respective second electrodes 34.

The wires 42 are formed on the insulating layer 41. The wires 42 aredrawn out from the respective second electrodes 34 of the piezoelectricelements 31. Each of the wires 42 is formed of aluminum (Al), forexample. As illustrated in FIG. 5, one end portion of each of the wires42 is disposed so as to overlap an end portion of the second electrode34 disposed on a corresponding one of the piezoelectric layers 33. Eachof the wires 42 is conductive with the corresponding second electrode 34by a through electrically-conductive portion 48 that extends through theprotecting layer 40 and the insulating layer 41.

Each of the wires 42 corresponding to the respective piezoelectricelements 31 extends rightward or leftward. That is, a direction in whicheach of the wires 42 extends (hereinafter may be referred to as “wireextending direction”) is orthogonal to the nozzle arrangement direction.Specifically, as illustrated in FIG. 3, the wires 42 extend rightwardfrom the respective piezoelectric elements 31 constituting the right twopiezoelectric element groups 39 k, 39 y of the four piezoelectricelement groups 39, and the wires 42 extend leftward from the respectivepiezoelectric elements 31 constituting the left two piezoelectricelement groups 39 c, 39 m of the four piezoelectric element groups 39.

Each of the driving contacts 46 is provided on an end portion of acorresponding one of the wires 42, which end portion is located on anopposite side of the wire 42 from its portion on which the secondelectrode 34 is disposed. The driving contacts 46 are arranged in a rowin the front and rear direction at each of a right end portion and aleft end portion of the piezoelectric actuator 22. That is, thedirection in which the driving contacts 46 are arranged (hereinafter mayalso referred to as “contact arrangement direction”) is parallel withthe nozzle arrangement direction. In the present embodiment, the nozzles24 forming the nozzle group 27 of each color are arranged at intervalsof 600 dpi (=42 μm). Also, each of the wires 42 extends rightward orleftward from the piezoelectric element 31 corresponding to the nozzlegroups 27 associated with corresponding two colors. Accordingly, at eachof the right end portion and the left end portion of the piezoelectricactuator 22, the driving contacts 46 are arranged at very shortintervals of a half of those of the nozzles 24 of each nozzle group 27,that is, the driving contacts 46 are arranged at the intervals of about21 μm.

The two ground contacts 47 are respectively disposed in front of and ata rear of the driving contacts 46 arranged in a row in the front andrear direction. Each of the ground contacts 47 has a larger contactingarea than each of the driving contacts 46. Each of the ground contacts47 is connected to the common electrode 36 via a corresponding one ofconducting portions 49 (see FIGS. 10A and 10B) which extends through theprotecting layer 40 and the insulating layer 41 located just under theground contact 47.

As described above, the driving contacts 46 and the ground contacts 47disposed on the right end portion and the left end portion of thepiezoelectric actuator 22 are exposed from the protector 23. The twoCOFs 50 are respectively joined to the right end portion and the leftend portion of the piezoelectric actuator 22. Each of the drivingcontacts 46 is connected to a corresponding one of the driver ICs 51 viaa corresponding one of the individual contacts 54 and a correspondingone of the individual wires 52 of the COFs 50. A drive signal issupplied from the driver IC 51 to the driving contacts 46. Each of theground contacts 47 is connected to a corresponding one of the groundcontacts 55 of the COFs 50. A ground potential is applied from theground contact 55 to the ground contact 47. Detailed constructions ofthe driving contacts 46 and the ground contacts 47 of the piezoelectricactuator 22 and electric connection of these contacts 46, 47 and thecontacts 54, 55 of the COF 50 will be described later.

As illustrated in FIG. 5, the wire protecting layer 43 is disposed so asto cover the wires 42. The wire protecting layer 43 increases insulationbetween the wires 42. Also, the wire protecting layer 43 inhibitsoxidation of a material, e.g., Al, of the wires 42. The wire protectinglayer 43 is formed of silicon nitride (SiNx), for example.

As illustrated in FIGS. 5 and 6, in the present embodiment, each of thesecond electrodes 34 is exposed from the protecting layer 40, theinsulating layer 41, and the wire protecting layer 43 except itsperipheral portion. That is, deformation of the piezoelectric layers 33is not hindered by the protecting layer 40, the insulating layer 41, andthe wire protecting layer 43.

Joined Portions of Piezoelectric Actuator and COF

There will be next explained a detailed construction of the joinedportions of the piezoelectric actuator 22 and each of the COFs 50.

As described above, the driving contacts 46 and the two ground contacts47 are arranged in the front and rear direction at each of the right endportion and the left end portion of the piezoelectric actuator 22. Theend portions of the respective COFs 50 are respectively joined to theright end portion and the left end portion of the piezoelectric actuator22 with a conductive adhesive 60.

As illustrated in FIGS. 8A and 10A, the conductive adhesive 60 is formedby mixing conductive particles 62 into a thermosetting adhesive 61formed of epoxy resin, for example. The epoxy resin is used for thethermosetting adhesive 61. Each of the conductive particles 62 is aspherical particle with a diameter D ranged between 3-5 μm, for example.The conductive adhesive 60 is generally used in the form of a film or apaste. One example of the film is an anisotropic conductive film (ACF),and one example of the paste is an anisotropic conductive paste (ACP).The conductive adhesive 60 is provided between the piezoelectricactuator 22 and each of the COFs 50 at an area elongated in the frontand rear direction across the contacts 46, 47 (the contacts 54, 55). TheCOFs 50 are pressed against the piezoelectric actuator 22 in this statewhile heating the conductive adhesive 60. As a result, the thermosettingadhesive 61 is hardened, so that the piezoelectric actuator 22 and eachof the COFs 50 is mechanically joined to each other, and the contactsare electrically connected between the piezoelectric actuator 22 andeach of the COFs 50 by the conductive particles 62 contained in theadhesive 60.

In some cases, incidentally, the conductive particles 62 may flow out toareas around the contacts together with the adhesive at heating in thejoining using the conductive adhesive 60, leading to poor connection. Toimprove reliability of electric connection, the present embodimentemploys a structure for preventing an outflow of the conductiveparticles 62 contained in the adhesive 60.

Specifically, as illustrated in FIGS. 7-8B, each of the driving contacts46 is provided with two protrusions 63 arranged in the front and reardirection and a recess 64 interposed between the two protrusions 63.Each of the protrusions 63 is elongated in the right and left direction.Accordingly, the recess 64 interposed between the two protrusions 63also has an elongated shape with its length in the right and leftdirection is longer than its width in the front and rear direction.

Each of the driving contacts 46 is joined to a corresponding one of theindividual contacts 54 of the COF 50 with the conductive adhesive 60located in the recess 64 in a state in which the two protrusions 63 arein direct contact with the individual contact 54 of the COF 50. Theconductive particles 62 located in the conductive adhesive 60 are caughtby the recess 64 of the driving contact 46, and the contacts 46, 47conduct each other also by the conductive particles 62 located in therecess 64.

There will be specifically explained constructions of the protrusions 63and the recess 64 of the driving contact 46. As illustrated in FIGS.7-8B, a distal end portion of each of the wires 42 extending from therespective second electrodes 34 is bifurcated into two portions. Thatis, the distal end portion of the wire 42 has two electricallyconductive portions 42 a spaced apart from in the front and reardirection and each extending in the right and left direction. The twoelectrically conductive portions 42 a are connected to each other bycoupling portions 42 b, 42 c respectively provided at a basal endportion of the driving contact 46 and a central portion of the drivingcontact 46 in its longitudinal direction. The wire protecting layer 43covering the wire 42 also covers the two electrically conductiveportions 42 a.

Each of the driving contacts 46 is formed of, e.g., gold (Au) andoverlaps the two electrically conductive portions 42 a of thecorresponding wire 42 via the wire protecting layer 43. Morespecifically, each driving contact 46 is disposed so as to overlap theentire two electrically conductive portions 42 a and a region locatedbetween the two electrically conductive portions 42 a. As illustrated inFIG. 8B, the driving contact 46 conducts with the coupling portion 42 bby a conducting portion 67 extending through the wire protecting layer43. That is, the driving contact 46 is connected to the wire 42 via theconducting portion 67, the coupling portion 42 b, and the twoelectrically conductive portions 42 a.

In the above-described construction, each of the protrusions 63 isformed by a corresponding one of the electrically conductive portions 42a, a portion of the wire protecting layer 43 which covers theelectrically conductive portion 42 a, and a portion the driving contact46 which covers the electrically conductive portion 42 a. The recess 64is formed by a portion of the driving contact 46 which is locatedbetween the two electrically conductive portions 42 a. As is apparentfrom FIGS. 8A and 8B, the recess 64 is partially shallow at its regionoverlapping the coupling portion 42 c.

Like the driving contact 46, as illustrated in FIGS. 9-10B, each of theground contacts 47 includes two protrusions 65 and a recess 66. Each ofthe ground contacts 47 is joined to a corresponding one of the groundcontacts 55 of the COF 50 with the conductive adhesive 60 located in therecess 66 in a state in which the two protrusions 65 are in contact withthe ground contact 55 of the COF 50. While the ground contact 47 is acontact with what is called a solid pattern expanding in plan view inFIG. 9, the ground contact 47 may be divided into a plurality of smallcontacts arranged at the same intervals as those of the driving contacts46. A strength of joining between the ground contact 47 and the groundcontact 55 of the COF 50 is increased by the adhesive 60 having enteredregions each between adjacent two of the small contacts.

There will be next explained constructions of the protrusions 65 and therecess 66 of the ground contact 47. Drawn-out wires 58 for the commonelectrode 36 are formed on the insulating layer 41 with the wires 42.Each of the drawn-out wires 58 conducts with the common electrode 36located under the protecting layer 40, by a corresponding one of theconducting portions 49 which extends through the insulating layer 41 andthe protecting layer 40. Two electrically conductive portions 58 a areformed on a distal end portion of each of the drawn-out wires 58. Thetwo electrically conductive portions 58 a are connected to each other bycoupling portions 58 b, 58 c. The two electrically conductive portions58 a are also covered with the wire protecting layer 43 on which theground contact 47 formed of, e.g., gold (Au) is disposed. The groundcontact 47 conducts with the coupling portion 58 b by a conductingportion 68 extending through the wire protecting layer 43. That is, theground contact 47 is connected to the common electrode 36 via theconducting portion 68, the coupling portion 58 b, the two electricallyconductive portions 58 a, the drawn-out wires 58, and the conductingportion 49.

In the above-described construction, each of the protrusions 65 isformed by a corresponding one of the electrically conductive portions 58a, a portion of the wire protecting layer 43 which covers theelectrically conductive portion 58 a, and a portion of the groundcontact 47 which covers the electrically conductive portion 58 a. Therecess 66 is formed by a portion of the ground contact 47 which islocated between the two electrically conductive portions 58 a.

The area of each of the protrusions 65 of the ground contact 47 islarger than that of each of the protrusions 63 of the driving contact46. The area of the recess 66 of the ground contact 47 is also largerthan the area of the recess 64 of the driving contact 46. Specifically,the width Wa′ of the protrusion 65 of the ground contact 47 in the frontand rear direction is greater than the width Wa of the protrusion 63 ofthe driving contact 46 in the front and rear direction. The width Wb′ ofthe recess 66 of the ground contact 47 in the front and rear directionis greater than the width Wb of the recess 64 of the driving contact 46in the front and rear direction.

As described above, the ground contact 47 is connected to the commonelectrode 36. A large current may temporarily flow in the commonelectrode 36 when a plurality of the piezoelectric elements 31 aredriven at the same time. In this case, a difference in length amongpassages connected to the common electrode 36 increases a difference indrop of voltage in the passages connected to the common electrode 36among the piezoelectric elements 31, resulting in increase in differencein amount of displacement among the piezoelectric elements 31. Tosuppress this phenomenon, the resistance of the passages connected tothe common electrode 36 is preferably made as small as possible. Thus, aresistance of connection between the ground contact 47 and the groundcontact 55 is also preferably made small. That is, the area of theprotrusion 65 of the ground contact 47 which contacts the ground contact55 of the COF 50 is preferably large, and the area of the recess 66 ofthe ground contact 47 in which the conductive particles 62 are caught isalso preferably large.

In the present embodiment as described above, each of the drivingcontacts 46 and the ground contacts 47 has the protrusions and therecess. However, although the contacting area, etc, is different in somedegree between the driving contacts 46 and the ground contacts 47, thereis no large difference in electric connection between the contacts ofthe piezoelectric actuator 22 and the contacts of the COF 50. Thus, thefollowing explanation will be provided, taking the driving contacts 46as an example except cases which requires references to the groundcontacts 47, in particular.

There will be explained a process of producing the ink-jet head 4 withreference to FIGS. 11A-12I, mainly focusing on forming of the drivingcontacts 46 and joining of the COF 50. It is noted that the followingsteps A-I respectively correspond to FIGS. 11A-12I.

In step A, the vibration layer 30 is formed by performing an oxidationprocessing or a nitriding processing on a surface of a silicon singlecrystal base that is to become the passage definer 21. In step B, thefirst electrodes 32 (the common electrode 36), the piezoelectric layers33, and the second electrodes 34 are formed on the vibration layer 30 bydeposition and etching to form the piezoelectric elements 31. In step C,the protecting layer 40 and the insulating layer 41 are formed so as tocover the piezoelectric layers 33, and patterning is performed byetching.

In step D, the wires 42 formed of, e.g., aluminum (Al) are formed on theinsulating layer 41. Specifically, step D is performed by forming an Allayer on the insulating layer 41 and then patterning and etching this Allayer. In this patterning, the two electrically conductive portions 42 aare formed on the distal end portion of each wire 42. In step E, thewire protecting layer 43 is formed on the wires 42 and patterned. Thewire protecting layer 43 is also formed so as to cover the twoelectrically conductive portions 42 a of the distal end portion of eachwire 42. In step F, the driving contacts 46 formed of, e.g., gold (Au)is formed by plating on the wire protecting layer 43 covering theelectrically conductive portions 42 a. As a result, each of the drivingcontacts 46 is shaped to have the two protrusions 63 and the recess 64(see FIGS. 8A and 8B).

In step G, the protector 23 is joined to the piezoelectric actuator 22so as to cover the piezoelectric elements 31. In step H, the passagedefiner 21 is polished to reduce its thickness to an appropriatethickness, and then the pressure chambers 26 are formed by etching. Instep I, the COF 50 is joined with the conductive adhesive 60 to the endportion of the piezoelectric actuator 22 on which the driving contacts46 and the ground contacts 47 are disposed. Specifically, the conductiveadhesive 60 (ACF or ACP) is provided between the piezoelectric actuator22 and the COF 50, and then the COF 50 is pressed against the conductiveadhesive 60 using a heater plate 58 placed on an upper surface of theCOF 50.

This pressing of the COF 50 using the heater plate 58 heats andcompresses the conductive adhesive 60 between each of the drivingcontacts 46 and the corresponding individual contact 54. In thisprocess, as illustrated in FIGS. 8A and 8B, the thermosetting adhesive61 is partly melted and pushed to an outside from an area locatedbetween each pair of contacts, and the two protrusions 63 of eachdriving contact 46 and the corresponding individual contact 54 of theCOF 50 are brought into contact with each other. The thermosettingadhesive 61 is hardened in this state, whereby the COF 50 ismechanically joined to the piezoelectric actuator 22 in a state in whicheach driving contact 46 and the corresponding individual contact 54conduct with each other. The conductive particles 62 contained in theconductive adhesive 60 are caught in the recess 64 interposed betweenthe two protrusions 63. With this construction, the number of theconductive particles 62 contained in the conductive adhesive 60 need notbe increased so much to catch the conductive particles 62 in the areabetween the two contacts 46, 47. This construction is particularlyeffective to increase electric reliability while preventing shortsbetween adjacent contacts in the construction in which intervals of thearrangement of the driving contacts 46 is very short as in the presentembodiment.

In the present embodiment, each driving contact 46 and the correspondingindividual contact 54 of the actuator device 25 are in contact with eachother in two configurations (i) and (ii). The configuration (i) isdirect contact of the protrusions 63 with the individual contacts 54.The configuration (ii) is contact of the conductive particles 62 caughtin the recess 64 with the individual contacts 54.

If each driving contact 46 and the corresponding individual contact 54conduct with each other only in the configuration (i) (the directcontact of the protrusions 63), when a mechanically bonding force of theadhesive 61 is lowered due to time-dependent deterioration of theadhesive 61 around the driving contacts 46, a conduction failure mayoccur due to separation of the protrusions 63 from the individualcontact 54. In this regard, in the present embodiment, conduction iscaused not only by the direct contact of the protrusions 63 but also bythe conductive particles 62 located in the recess 64. Thus, even if theprotrusions 63 are separated from the individual contact 54, theconducting state is maintained by the conductive particles 62. That is,the actuator device has a long useful life with high resistance to thetime-dependent deterioration.

If each driving contact 46 and the corresponding individual contact 54conduct with each other only by the conductive particles 62 as in theconfiguration (ii), the conduction ceases when the conductive particles62 flow out from between the two contacts 46, 47. In this regard, in thepresent embodiment, conduction is caused not only by the direct contactof the protrusions 63 but also by the conductive particles 62, resultingin improved reliability of electric connection. Also, connectionresistance is reduced.

In the present embodiment, the following configurations are employedfrom the viewpoint of improving reliability of electric connectionbetween the contacts.

In the case where the number of the conductive particles 62 contained inthe conductive adhesive 60 interposed between the piezoelectric actuator22 and the COF 50 per area A is defined as n, and the base area of eachrecess 64 is defined as A1, a relationship “A1≥A/n” is established. Inthe case where the area of the recess 64 is greater than or equal to thevalue A/n, one or more conductive particles 62 are held in each recess64 based on a simple calculation. That is, the conductive particle orparticles 62 are more easily caught in the recess 64.

Specifically, in the case where the conductive adhesive 60 is ananisotropic conductive film (ACF), the number of the conductiveparticles 62 contained in the film per area A only needs to be n. In thecase where the conductive adhesive 60 is an anisotropic conductive paste(ACP), the number of the conductive particles 62 contained in the pasteper area A in a state in which the paste is applied to the surface ofthe contact only needs to be n.

As illustrated in FIGS. 8A and 8B, the two protrusions 63 of the drivingcontact 46 are in contact with the individual contact 54. In thisconstruction, the driving contact 46 is in direct contact with theindividual contact 54 at two positions, resulting in improvedreliability of conduction. Also, the recess 64 located between the twoprotrusions 63 is closed by the individual contact 54, making itdifficult for the conductive particles 62 to flow out from the recess64.

The width W0 of the individual contact 54 in the front and reardirection is greater than the width W1 of the driving contact 46 in thefront and rear direction for reliable contact of the two protrusions 63of the driving contact 46 with the individual contact 54. Morespecifically, the width W0 of the individual contact 54 is preferablygreater than or equal to twice the width W1 of the driving contact 46.Even in the case where the width W0 of the individual contact 54 isslightly shorter than the width W1, the individual contact 54 is inreliable contact with the two protrusions 63 in the case where the widthW0 is greater than the distance Wp between outer ends of the twoprotrusions 63 of the driving contact 46.

In the case where the width of the recess 64 is less than the diameterof the conductive particle 62, there is a higher possibility that theconductive particle 62 is pushed out from the recess 64 at joiningwithout being caught in the recess 64. In order to reliably catch theconductive particle 62 in the recess 64, the width Wb of the recess 64in the front and rear direction is greater than or equal to the diameterD of the conductive particle 62 before joining in the presentembodiment. Specifically, the width Wb of the recess 64 is preferablygreater than or equal to twice the diameter D of the conductive particle62. This sufficient width of the recess 64 can catch the conductiveparticle 62 more reliably. Also, it is possible to catch two or moreconductive particles 62 in each recess 64.

In the case where the area of each protrusion 63 is too large withrespect to the recess 64 in FIGS. 8A and 8B, the conductive particle 62may be located on the protrusion 63, making it difficult for theconductive particle 62 to contact the contacts 46, 47 in the recess 64.From this viewpoint, the width Wa of the protrusion 63 is preferablyless than the width Wb of the recess 64. This discussion is true to theground contacts 47 illustrated in FIGS. 10A and 10B, the width Wa′ ofthe protrusion 65 is preferably less than the width Wb′ of the recess66.

If the width Wb of the recess 64 is made too large, the width W1 of thedriving contact 46 including the recess 64 is also increased. In thiscase, a distance between the driving contact 46 and another drivingcontact 46 next to the driving contact 46 is short, which may lead toshorts therebetween. If the distance is made large in order to preventshorts, the size of the actuator 22 increases in the front and reardirection. Accordingly, the width Wb of the recess 64 in the front andrear direction is preferably less than or equal to ten times thediameter D of the conductive particle 62. Furthermore, the width W1 ofthe driving contact 46 in the front and rear direction is alsopreferably less than or equal to ten times the diameter D of theconductive particle 62.

The conductive particle 62 caught in the recess 64 is preferablycompressed between the driving contact 46 and the individual contact 54and in contact with both of the driving contact 46 and the individualcontact 54 by elastic resilience. From this viewpoint, in the presentembodiment, the depth d of the recess 64 is less than the diameter D ofthe conductive particle 62. Specifically, in the case where the depth dof the recess 64 is less than or equal to three fifths of the diameter Dof the conductive particle 62, the conductive particle 62 is compressedin an appropriate degree. In FIG. 8A, the two-dot chain line indicatesthe conductive particle 62 at a time before joining (beforecompression), and the solid line indicates the conductive particle 62 ata time after joining (after compression). The above-described diameter Dof the conductive particle 62 indicates the diameter of the conductiveparticle 62 before the conductive particle 62 is compressed. In theabove-described construction, the conductive particle 62 located in therecess 64 is reliably compressed between the driving contact 46 and theindividual contact 54 and reliably in contact with both of the drivingcontact 46 and the individual contact 54, resulting in increasedreliability of electric connection.

However, if the depth d of the recess 64 is too small, the conductiveparticle 62 easily flows out from the recess 64. Accordingly, the depthd of the recess 64 is preferably greater than or equal to one fifth ofthe diameter D of the conductive particle 62.

While the relationship between the width Wb of the recess 64 and thediameter D of the conductive particle 62 is described above in relationto the catch of the conductive particle 62, there is another problem inwhich in the case where the width Wb of the recess 64 is not largeenough with respect to the diameter D of the conductive particle 62,when the COF 50 is pressed against the conductive particle 62, theconductive particle 62 cannot be widened laterally and is not easilycompressed vertically. That is, the width Wb of the recess 64 ispreferably large enough with respect to the diameter of the conductiveparticle 62 also from the viewpoint of reliably compressing theconductive particle 62. Specifically, the width Wb of the recess 64 ispreferably greater than or equal to twice the diameter D of theconductive particle 62.

In the present embodiment, the recess 64 has an elongated shape whoselength in the right and left direction is longer than its width in thefront and rear direction. Also, only one recess 64 is formed for each ofthe driving contacts 46 in the front and rear direction. With theseconstructions, the width Wb of the recess 64 is short in the front andrear direction in which the driving contacts 46 are arranged, so thatthe width W1 of the driving contact 46 is small. Since the recess 64 islong in the right and left direction, it is possible to catch manyconductive particles 62 in the recess 64. Also, although the recess 64is formed in each of the driving contacts 46, intervals at which thedriving contacts 46 are arranged can be made short. In particular, thepresent embodiment employs the above-described construction because thedriving contacts 46 need to be arranged in a row though the nozzles 24of the two nozzle groups 27 corresponding to the driving contacts 46 arearranged at the high density of 600 dpi.

In the present embodiment, the driving contact 46 of the piezoelectricactuator 22 is formed with the protrusions 63 and the recess 64.However, effects similar to the above-described effects are obtainedeven in a construction in which protrusions and a recess are formed onand in each of the individual contacts 54 of the COF 50. However,forming of the protrusions and the recess on and in each of the contactsrequires patterning at intervals shorter than the intervals at which thecontacts are arranged. Specifically, in the present embodiment, the twoelectrically conductive portions 42 a for forming the two protrusions 63are formed on the distal end portion of each of the wires 42. The twoelectrically conductive portions 42 a are formed at a considerably smalldistance of a half of the intervals in which the wires 42 are arranged.

Focusing on achieving fine pitches, patterning is in general more easilyperformed on a silicon single crystal base than a wire base such as theCOF 50 at the current technological level. That is, fine patterns aremore easily formed on the silicon base than on the wire base.Accordingly, if the recess and the protrusions may be formed in and onany of each contact of the piezoelectric actuator 22 and each contact ofthe COF 50, the protrusions 63 and the recess 64 are more easily formedon and in each of the driving contacts 46 of the piezoelectric actuator22.

As described in the explanation for the producing process, each wire 42having the two electrically conductive portions 42 a is formed ofaluminum (Al) and patterned by etching of the Al layer in the presentembodiment. The patterning using etching enables formation of wirepatterns at a high definition. In contrast, the driving contacts 46 areformed of gold (Au) and are generally formed by plating. The precisionof patterning by plating is less than that of patterning by etching.That is, in the present embodiment, the driving contact 46 formed of amaterial unsuitable for fine pitches is formed over the electricallyconductive portions 42 a formed by etching at fine pitches, whereby thetwo protrusions 63 and the recess 64 are formed.

However, aluminum is subject to oxidation when compared with gold. Thus,in the present embodiment, the two electrically conductive portions 42 aare covered with the wire protecting layer 43, and the driving contact46 is formed thereon. This construction inhibits oxidation of theelectrically conductive portions 42 a.

In the embodiment described above, the ink-jet head 4 is one example ofa liquid ejection apparatus. The piezoelectric actuator 22 is oneexample of an actuator. The front and rear direction, i.e., each of thenozzle arrangement direction and the contact arrangement direction isone example of a first direction. The right and left direction, i.e.,the wire extending direction parallel with the upper surface of thepiezoelectric actuator 22 on which the contacts 46 are disposed andorthogonal to the contact arrangement direction is one example of asecond direction. The COF 50 is one example of a wire member. Each ofthe driving contacts 46 and the ground contacts 47 of the piezoelectricactuator 22 is one example of a first contact. Each of the individualcontacts 54 and the ground contacts 55 of the COF 50 is one example of asecond contact. The wire protecting layer 43 covering the twoelectrically conductive portions 42 a is one example of an insulatinglayer.

There will be next explained modifications of the embodiment. It isnoted that the same reference numerals as used in the above-describedembodiment are used to designate the corresponding elements of themodifications, and an explanation of which is dispensed with.

In the above-described embodiment, each of the driving contacts 46 andthe ground contacts 47 of the piezoelectric actuator 22 has theprotrusions and the recess. However, only one of each of the drivingcontacts 46 and each of the ground contacts 47 may have the protrusionsand the recess.

In the above-described embodiment, the three insulating layers, namely,the protecting layer 40, the insulating layer 41, and the wireprotecting layer 43, are formed on the piezoelectric layers 33, butthese layers may be removed as needed. For example, in the case wherethe wires connected to the second electrodes 34 are formed of a highlystable material such as gold (Au), the insulating layer 41 and theprotecting layer 43 may not be provided.

The shapes of the protrusions and the recess formed on and in eachcontact are not limited to those in the above-described embodiment. Forexample, the following first-fourth modifications may be provided.

In the first modification, three or more protrusions and two or morerecesses may be formed on and in each contact. Increase in the number ofprotrusions increases the direct contact area, resulting in higherreliability of electric connection. Also, the connection resistance isreduced. Furthermore, increase in the number of recesses increases thenumber of the conductive particles 62 to be caught, resulting in higherreliability of electric connection.

In the above-described embodiment, as illustrated in FIGS. 8A and 8B,the width of the individual contact 54 of the COF 50 is greater than thewidth of the driving contact 46 of the piezoelectric actuator 22. In asecond modification, as illustrated in FIG. 13A, the width of anindividual contact 54A of the COF 50A may be less than that of thedriving contact 46 of the piezoelectric actuator 22. Alternatively, asillustrated in FIG. 13B, only one of the two protrusions 63 of thedriving contact 46 may be in contact with the individual contact 54B.Also in this construction, most of the recess 64 located between the twoprotrusions 63 is closed by a COF 50B, making it difficult for theconductive particles 62 to flow out from the recess 64.

In the above-described embodiment, the depth of the recess 64 is lessthan the diameter of the conductive particle 62. In a thirdmodification, however, the depth of the recess may be greater than thediameter of the conductive particle 62. Also in this construction, it ispossible to compress the conductive particles 62 in the recess as longas two or more conductive particles 62 are caught in the recess.

In the above-described embodiment, as illustrated in FIG. 7, noprotrusion is formed to the right of the recess 64 (i.e., on one ofopposite sides of the recess 64 which is located nearer to a distal endof the contact 46 than the other), and a right end of the recess 64 isopen. In a fourth modification, however, a protrusion may be formed onone of opposite sides of the recess which is located nearer to a distalend of the contact than the other. In this construction, the recess issurrounded by the protrusions, making it difficult for the conductiveparticles to flow out from the recess.

While the two protrusions 63 are formed by the bifurcated shape of thedistal end portion of the wire 42 in the above-described embodiment,protrusions and a recess may be formed on and in the contact in othermethods.

In a modification illustrated in FIG. 14A, a recessed layer portion 70is formed by etching an upper surface of a vibration layer 30C. Adriving contact 46C is disposed so as to cover the recessed layerportion 70. In this construction, a portion of the driving contact 46Cwhich overlaps the recessed layer portion 70 serves as a recess 64C.Protrusions 63C are constituted by (i) portions of the vibration layer30C which are located in front of and at a rear of the layer portion 70and (ii) portions of the driving contact 46C which are respectivelylocated just above the portions of the vibration layer 30C.

FIG. 14B illustrates yet another modification in which a recessed layerportion is formed by etching the piezoelectric layer instead of thevibration layer. In this modification, a piezoelectric layer 33D locatedover the vibration layer 30 extends to an end portion of the passagedefiner 21. The piezoelectric layer 33D is etched to form a recessedlayer portion 71. A driving contact 46D is disposed so as to cover therecessed layer portion 71. In this construction, a portion of thedriving contact 46D which overlaps the recessed layer portion 71 servesas a recess 64D. Protrusions 63D are constituted by (i) portions of thepiezoelectric layer 33D which are located in front of and at a rear ofthe layer portion 71 and (ii) portions of the driving contact 46D whichare respectively located just above the portions of the piezoelectriclayer 33D.

FIG. 14C illustrates yet another modification in which a driving contact46E disposed on the vibration layer 30 includes a conductive layer 72and two conductors 73. The two conductors 73 are disposed on theconductive layer 72 so as to be spaced apart from each other in thefront and rear direction. In this modification, protrusions 63E areconstituted by the conductors 73 and portions of the conductive layer 72which are located just below the respective conductors 73. A portion ofthe conductive layer 72 which is interposed between the two conductors73 serves as a recess 64E.

FIG. 14D illustrates yet another modification in which etching, plasmaprocessing, and/or other similar processings may be performed on asurface of a driving contact 46F, to which the individual contact 54 isconnected, such that the driving contact 46F has a rough surface 74 witha surface roughness enough to catch the conductive particles 62. Forexample, a desired surface roughness of the surface of the drivingcontact may be achieved by changes of an etch rate of wet etching (seeJapanese Patent Application Publication No. 2012-222025).

Protrusions 63F and recesses 64F having various shapes are formed on andin the rough surface 74. The surface roughness (arithmetic averageroughness) Ra of the rough surface 74 is preferably less than thediameter D of the conductive particle 62 in order to compress theconductive particles 62 in the recesses 64F of the rough surface 74. Ifthe surface roughness Ra is too small, the recesses 64F cannot catch theconductive particles 62. Thus, the surface roughness Ra is preferablygreater than or equal to one fifth of the diameter D of the conductiveparticle 62.

In the above-described embodiment, the two protrusions 63 of each of thedriving contacts 46 are arranged in the front and rear directioncoinciding with the direction in which the driving contacts 46 arearranged. However, two or more protrusions may be arranged in adirection orthogonal to the direction in which the driving contacts arearranged. In this construction, the width of each of the contacts in thecontact arrangement direction is large in many cases, leading toincrease in intervals at which the contacts are arranged. However, thelarger width of each contact results in higher peel strength of the COF.

In the above-described embodiment, the protrusions 63 and the recess 64are formed on and in each of the driving contacts 46 of thepiezoelectric actuator 22, but protrusions and a recess are formed onand in each contact of the COF. For example, in a modificationillustrated in FIG. 15, an individual contact 54G of a COF 50G which isconnected to a driving contact 46G of a piezoelectric actuator 22Gincludes a conductive layer 76 and two conductors 77. The two conductors77 are disposed on the conductive layer 76 so as to be spaced apart fromeach other in the front and rear direction. In this construction,protrusions 63G are constituted by the conductors 77 and portions of theconductive layer 76 which are located just below the respectiveconductors 77. Also, a portion of the conductive layer 76 which islocated between the two conductors 77 serves as a recess 64G.

The arrangement of the driving contacts and the ground contacts in oneink-jet head is not limited to the arrangement in the above-describedembodiment. For example, the ink-jet head may be configured such thatall the wires of the piezoelectric elements are drawn in one direction,and all the driving contacts are arranged in a row at one end portion ofthe piezoelectric actuator. The ink-jet head may be configured such thatall the wires of the piezoelectric elements are drawn toward a centralportion of the piezoelectric actuator in the scanning direction, and allthe driving contacts are arranged in a row at the central portion of thepiezoelectric actuator. The number of the ground contacts is not limitedto two and may be one, or three or more.

The ink-jet head 4 in the above-described embodiment is a serial headconfigured to eject the ink while moving in the widthwise direction ofthe recording sheet 100. However, the present disclosure may be appliedto a line head having nozzles arranged in the widthwise direction of thesheet.

While the present disclosure is applied to the ink-jet head configuredto eject the ink onto the recording sheet to record an image in theabove-described embodiment, the present disclosure may be applied toactuator devices used for purposes other than liquid ejection. Also, theactuator is not limited to the piezoelectric actuator including aplurality of piezoelectric elements. For example, the actuator may be anactuator including a heater as a drive element which causes driving byutilizing a heat generated when a current passes through the heater.

What is claimed is:
 1. A head, comprising: an actuator comprising atleast one first contact wherein at least two protrusions and at leastone recess are formed on and in the at least one first contact, the atleast two protrusions being arranged in a first direction parallel witha placement surface of each of the at least one first contact, the atleast one recess being interposed between the at least two protrusions,and wherein a plurality of first contacts as the at least one firstcontact are arranged at an interval of less than or equal to 21 μm. 2.The head according to claim 1, wherein the actuator comprises apiezoelectric layer with a thickness between 1.0 μm and 2.0 μm.
 3. Thehead according to claim 1, further comprising a wire member comprisingat least one second contact respectively connected to the at least onefirst contact, wherein one of (i) each of the at least one first contactand (ii) each of the at least one second contact is each of at least oneparticular contact, and another of (i) each of the at least one firstcontact and (ii) each of the at least one second contact is each of atleast one specific contact, wherein the at least two protrusions and theat least one recess are formed on and in the at least one particularcontact, the at least two protrusions being arranged in the firstdirection parallel with the placement surface of each of the at leastone particular contact, and wherein the at least one particular contactis respectively joined to the at least one specific contact in a statein which each of the at least two protrusions is in contact with acorresponding one of the at least one specific contact.
 4. The headaccording to claim 3, wherein each of the at least two protrusions is incontact with a corresponding one of the at least one specific contact.5. The head according to claim 4, wherein a width of each of the atleast one specific contact in the first direction is greater than awidth of each of the at least one particular contact in the firstdirection.
 6. The head according to claim 5, wherein the width of eachof the at least one specific contact in the first direction is greaterthan or equal to twice the width of each of the at least one particularcontact in the first direction.
 7. The head according to claim 1,wherein the at least one first contact and the at least one secondcontact are bonded to each other with a conductive adhesive.
 8. The headaccording to claim 7, wherein the conductive adhesive comprises aconductive particle with a diameter between 3 μm and 5 μm.
 9. The headaccording to claim 8, wherein where n is the number of conductiveparticles contained in the conductive adhesive per area A, and Al is anarea of each of the at least one recess, Al is greater than or equal toA/n.
 10. The head according to claim 8, wherein a width of each of theat least one recess in the first direction is greater than or equal to adiameter of the conductive particle.
 11. The head according to claim 10,wherein the width of each of the at least one recess in the firstdirection is greater than or equal to twice the diameter of theconductive particle.
 12. The head according to claim 10, wherein thewidth of each of the at least one recess in the first direction is lessthan or equal to ten times the diameter of the conductive particle. 13.The head according to claim 12, wherein a width of each of the at leastone particular contact in the first direction is less than or equal toten times the diameter of the conductive particle.
 14. The headaccording to claim 8, wherein a depth of each of the at least one recessis less than a diameter of the conductive particle.
 15. The headaccording to claim 14, wherein the depth of each of the at least onerecess is less than or equal to three fifths of the diameter of theconductive particle.
 16. The head according to claim 14, wherein thedepth of each of the at least one recess is greater than or equal to onefifth of the diameter of the conductive particle.
 17. The head accordingto claim 1, wherein a length of each of the at least one recess in asecond direction parallel with the placement surface and orthogonal tothe first direction is greater than that of each of the at least onerecess in the first direction.
 18. The head according to claim 17,wherein only one of the at least one recess is disposed in the firstdirection.